Synthesis of palladium complexes containing benzimidazole core and their catalytic activities in direct arylation of heteroaromatic species

Herein, we report the synthesis of four new palladium complexes containing a benzimidazole core and examine their catalytic activities in the direct arylation of heteroaromatic species with aryl bromides. The complexes were characterized by H-1 and C-13 NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. In the C-13 NMR spectra, NCHN peaks of Pd(II) complexes were observed between 143.2 and 144.9 ppm. Also, the structure of 2b was determined by single-crystal XRD analysis. The obtained data suggest that the lengths of the Pd-N and Pd-Cl bonds are like those of previous Pd complexes. Direct arylation reactions, using KOAc as base and DMAc as solvent under inert conditions, were carried out with the synthesized complexes in the presence of various aryl bromides, and 2-acetylthiophene, 2-furaldehyde, and 1-methylpyrole-2-carboxaldehyde. Moderate to high yields were obtained under 1% mol catalyst loading conditions. The results showed that electron-donating and electron-withdrawing substituents on the aryl halides may produce coupling products in good yields in the presence of 2a-d. These findings contribute to the synthesis and design of palladium complexes containing benzimidazole cores.